Method and apparatus for forming grinding wheels



Dec. 25, 1956 o. A. GUENTHER 2,775,073

METHOD AND APPARATUS FOR FORMING GRINDING WHEELS Filed June 17, 1955 INVENTOR ORRION A. UENTHER HIS ATTORNEYS METHOD AND APRARATUS FOR FORMING GRINDING WHEELS Orrion A. Guenther, Waynesville, Ohio, assignor to The National Cash Register Company, Dayton, Ohio, a corporation of Maryland Application June 17, 1955, Serial No. 516,295

Claims. (Cl. 51-283) This invention relates to the method of making accurately-ground profiles on diamond grinding wheels, and to apparatus therefor.

It is well known in the metal grinding art, particularly in the making of accurate dies and tools of tungsten carbide or metal of equivalent hardness, that it would be highly desirable to have a diamond grinding wheel with a periphery having a profile of highly accurate dimensions, so that an accurate cut of the desired contour could be made by a small number of passes of the grinding wheel. I

This invention provides means for profiling a resinbonded diamond grinding wheel, while it is still on the arbor on which it is to be used, to within .0002 of an inch of the specified dimensions.

The method, in general, includes the step of forming the desired profile, in reverse form, on the periphery of an aluminum oxide grinding wheel, of the ceramic bonded type, by use of a diamond shaping tool, and then bringing the so-formed and profiled ceramic aluminum oxide grinding wheel, rotating with a peripheral speed of from 1.2 inches to 3.2 inches per minute, against the diamond grinding wheel to be shaped while said diamond grinding wheel is traveling from 600 inches to 2,000 inches per minute on its periphery, which is far below its cutting speed. Generally speaking, the softer the bonding material is on the diamond grinding wheel, the slower the movement of the aluminum oxide wheel need be when moved into contact therewith.

In the making of contact between the two wheels, it is essential that the arbors of the two wheels be parallel, so that the profile of the diamond wheel may be accurately ground. Therefore, the invention provides a support for the two wheels and their arbors and driving means, whereby the aluminum grinding wheel may be brought into contact with the diamond grinding Wheel without change in the parallel relation of their arbors.

The aluminum oxide grinding Wheel, rotating slowly, brings a fresh peripheral surface thereof into contact with the diamond wheel very slowly, so that the accuracy of the cutting is maintained. The diamond wheel to be shaped, on the other hand, has a peripheral speed far below its cutting speed, which cutting speed would be about 40,000 inches per minute, so the aluminum oxide Wheel periphery is not quickly destroyed.

The rotation of the two wheels should be in the same sense, with the diamond wheel at the point of contact with the aluminum oxide wheel traveling downwardly, so that the abraded material falls to the base of the machine and will not accumulate at the point where the diamond wheel strikes the aluminum oxide wheel first. The abraded material may be recovered, as its diamond content is of value.

By this generally-described method of forming a profile on the periphery of the diamond grinding wheel, the very close tolerance of 0.0002 of an inch can be maintained with ease, and it is due to the fact that a fresh portion of the profile of the aluminum oxide wheel is always being nited States PatentO 2,775,078 Patented Dec. 25, 1956 moved to the contact point between wheels. By this meth- 0d, a diamond wheel maybe shaped with only a partially complete rotation of the aluminum oxide Wheel.

With these and incidental objects in view, the invention includes certain novel features of construction and processing steps, and combinations of them, a preferred form and embodiment of which is hereinafter described with reference to the drawing which accompanies and forms a part of this specification.

In the preferred embodiment of the invention, disclosed in the drawing, there is attached to the column 9, of the base of a grinding machine, a motor support plate 12, to which is strapped a motor 13, having an armature shaft 11, to which is secured a four-inch-diarneter diamond grinding wheel 10, the periphery of which is concentric with the shaft 11. The motor 13 has a normal speed of 3,500 revolutions a minute, which will give the periphery of the diamond wheel a linear speed of about 44,000 inches a minute. The grinding speed of the diamond wheel is preferably over 3,500 feet per minute. When it is desired to grind a profile on the periphery of the diamond wheel, a belt 14 is passed around a pulley 15, secured to the shaft 11, and a second, drive, pulley 16, secured on a shaft 17 of a reduction gear in mesh with a gear on the shaft of a low-speed motor 18, mounted on the plate 12. When the motor 18 is energized, the motor 13 is to be deenergized. The motor 18 is rated, through the reduction gearing and the pulleys, to drive the diamond wheel 10 at revolutions per minute, which gives the periphery of the diamond wheel a linear speed of about 1,250 inches per minute, which is below its cutting speed.

Mounted on a portion of the base (not shown) of the grinding machine is a reciprocating table 19, of the usual type, on which is mounted a magnetic chuck 20, for holding work to be ground, and a plate 21, supporting a motor 22, having a speed of 1,725 revolutions per minute, and a mechanism 23 for cutting a profile on the seven-inch-diameter ceramic bonded aluminum oxide grinding wheel 24. The wheel 24 is mounted on a shaft 25, journaled in a block 26, slidably mounted on an upright member 27, secured to the same plate 28 to which the mechanism 23 also is attached. The plate 28 has a dovetail flange 29, which rides in conforming guideways secured to the plate 21. The shafts 11 and 25 are parallel and of equal height above the table 19. An adjusting screw 30 is provided, so that the grinding wheel 24 may be moved so that its periphery is in alinement with that of the wheel 10. The shaft 25 has a pulley 31 secured thereto, by which it is connected by a belt 32 to a pulley 33 on the shaft of the motor 22. The pulleys 31 and 33 are so proportioned that the aluminum oxide grinding wheel 24 has a normal grinding speed of 3,450 revolutions per minute. This will give a peripheral speed of over 6,000 feet per minute. Allowances can be made for attaining this speed according to the diameter of the aluminum oxide wheel. The aluminum oxide wheel profiling mechanism 23 has a template-following arm 34, having a tracing stud 35, which is made to follow an enlarged template fastened to a bracket 36 whenever the periphery of the wheel 24 is to be dressed to the desired contour. The arm 34 is coupled to a pantograph mechanism within the casing of the mechanism 23 and moves in reduced motion, the scribing arm 35 having the diamond dressing point 36 secured therein. This pantograph mechanism is well known in the art.

After the aluminum oxide wheel 24 has been properly profiled, the diamond dressing point is moved away from the wheel 24, the motor 22 is deenergized, and the adjusting screw 38 is turned to move a motor support plate 39 to loosen the belt 32. The motor 13 is deenergized, if not already in that condition, the belt 14 is put in place, and the motor 18 is started to drive the diamond wheel 10 at 100 revolutions per minute in the direction of the arrow thereon.

Next, an auxiliary motor 40, which is pivoted at 4 to the block 26, is moved clockwise by, a thumbscrew 42 until its shaft 43, driven by reducing gears, bears on the periphery of a knurled disc 44, secured to the motor shaft 25. The end of the shaft 43 is equipped with a rubber sleeve to afford a friction drive. The motor 4 1 is equipped with reduction gears such that it will drive the aluminum oxide wheel about one tenth of a revolution per minute in the direction of the arrow thereon.

The table 19 then'is moved to bring the peripheries of the Wheels 10 and 24 together for sufiicient time to form the profile in the wheel 10, which in most instances will take only a part revolution of the wheel 24, after which the wheels are moved apart.

The preferred peripheral speeds of about 1,256 inches per minute for the diamond wheel and about 2.2 inches per minute for the aluminum oxide wheel, during the formation of the periphery of the diamond wheel, fall within the range of 600 inches to 2,000 inches per minute for the diamond wheel and 1.2 inches to 3.2 inches per minute for the aluminum oxide wheel.

At this rate of motion for the two wheels of the specified size, the aluminum oxide wheel will be able to cut several profiles into the diamond wheel before it completes a full rotation and has to be reshaped.

it is desirable to have the aluminum oxide wheel larger in diameter than the diamond wheel, because it will furnish more new peripheral surface than a smaller wheel and, hence, will be able to reshape the diamond wheel more often before being reshaped itself.

Allowances will have to be made for differences in the binder material for the diamond wheel, for depth of the profile cut to be made in the wheels, for the pressure exerted by the aluminum oxide against the diamond ticular preferred form disclosed herein, for it is susceptible of embodiment in various other forms.

What is claimed is:

1. The method of forming a profiled periphery on a diamond grinding wheel of the type which is bonded together with organic resin-like material, including the step of mounting the diamond wheel on the arbor on which it is to be used; causing the diamond wheel to be rotated at a peripheral speed of between 600 inches and 2,000 inches per minute; and bringing into contact with the periphery of the diamond wheel the periphery of a ceramic bonded aluminum oxide grinding wheel which is rotating at a peripheral speed of between 1.2 inches and 3.2 inches per minute, and whose periphery has been shaped with a profile the reverse of that which is to be formed on the diamond wheel.

2. The method of claim 1 in which the wheels rotate in the same direction with the surface of the diamond wheel periphery which is at the meeting point of the two wheels traveling downwardly.

3. The method of claim 1 in which the rotational axes of the wheels are kept parallel.

4. The method of conforming the peripheral surface of a resin-bonded diamond grinding wheel with that of an aluminum oxide grinding wheel, including the steps of rotating the diamond wheel on an axis at a peripheral speed of between 600 inches and 2,000 inches per minute;

'- rotating the aluminum oxide wheel, on a parallel axis,

wheel, and for such variables as are in the hands of the operator or which are brought about by the variations in the profile shape to be produced.

It will be appreciated that the apparatus for carrying out the method will have to be of a quality in respect to dimensions that will hold the wheels and their driving eluding the steps of rotating the diamond wheel at a speed greatly below its effective cutting speed and bringing. against its peripheral surface the peripheral surface of the aluminum oxide wheel while said aluminum oxide wheel is rotating in the same direction as the diamond wheel at from .0006 to .005 of the peripheral speed of the iamond wheel.

References Cited in the file of this patent UNITED STATES PATENTS 1,896,533 V uilleumier Feb. 7, 1933 2,473,670 Wilson June 21, 1949 2,528,621 Sweetser Nov. 7, 1950 2,644,681 Clark Jan. 5, 1 954 

